Rheostat



Patented .Maiz 15, 1927.

UNITED STATESPATENT OFFICE.

JOHN- ELLIOTT JENKINS, OF CHICAGO, ILLINOIS. v

nHEosTAT.

Application ld March 15, 1922. Serial'No. 543,859.

This invention relates to improvements in*- -rheo'stats of the sendingand receiving sets,

in order to secure the synchronism of wave length `that is essential to perfect transmis-J..

sion.

The rheostat of the present invention involves those features of construction which will permit of a gradual increase or decrease ofthe resistance, thus making it possible to obtain very minute variations throughout a considerable range of electrical activity.

In the drawing is illustrated a preferred embodiment of the invention, in which- Figure 1 is a view in front elevation of the rheostat, Y,

Figure 2 is a View inside elevation ofthe iFigure 3 is a view in vertical sect-ion, as taken on line 3-3 'of Figure 1, v

Figure 4 is an enlarged view showing more clearly the construction of the threaded block, resistance'element and contact member, and

Figure 5 is a view in front elevation eh9w ing the application of an indicating device for indicating the resistance in 'circuit lin every position of the contactv member.

The rlieostat is ordinarily mounted within 'convenient reach of the operator of the particular electrical apparatus of which it forms a part, being herein shown as supported upon an upright panel 1. Electrically, it is connected-in series with a battery or other source of current supply, and the particular elements into which the current Hows. In general, the rheostat comprises a cylindric block 2 made' of non-conductive substance,

- such as hard rubber, condensite, or the like,

said block being mounted in any suitable manner, as, forinstance, upon the rear face of; the panel 1 by means of' a screw passing through the block, and anchored in said panel. Cut or otherwise formed in the periphery or annular face of the block 2 are helical threads 2a extending transversely Ifrom the rear to the4 front side of the block,

and forming-between them similarly shaped grooves. These threads are preferably of the V-form of screw thread, although in the present disclosure a left hand thread is used; that is to say, the thread commences adjacent'the 4rear side of the block, traversing the face of the block toward the front side, land describing a true helix around the face thereo The use of the left handed thread rather than 'the right handed thread will be explained more in detail in connection with the operation of the rheostat.

Anchored to the front face of the block 2 are two radially disposed conductor plates 3 and 4, which are insulated from each other and arranged in diametrical alignment on opposite sides of the central axis of the block. The ends of the conductor bars terminato beyond the vthreaded periphery of the block in rearwardly bent fingers 3' and 4a respectively, there being mounted in said fingers terminal screws 5 5 whereby the 'terminal ends "of thel conductors 6 6EL are attached. As clearly shown in Figure l, the uppermost arm 3'terminates short ofthe central axis of the block 2, and is anchored thereto by means of a screw 7 whereas the lowermost arm 4 terminates in a rounded inner extremity surrounding the centralportion of the block, and provided with an ani nular opening 8 concentric with the axis, said end portion being further bifurcated by the provision of alongitudinal slot 9 extending inwardly from lthe end beyond the annular opening 8.` Another screw 10 se- Y cures the lower the block 2.

Extending centrally andv axially through plate 4 tothe front side of the block 2 is a bore into which is fittedaJ metal bushing or sleeve l1 terminating adjalcent the front side of the block in spaced lrelationwith the conductor arm 4, the purpose being that there shall be nondirect electrical connection therebetween. Journalled in the bushing ll is a` rotative spindle 12 which projects'outwardly from each Side of said block, and carries at its forward end'a thumb -wheel or knob 13, the same being located, as clearly shown in Figure 2, on the opposite side of the panell from the .block 2. The knob 13 is preferably made of a suitable insulating material, and is rovided with a cyiinic extension 13a 0 reduced diameter, extending toward the block 2, and inthe position shown in Figure 2, its end surface is spaced a short distance from the face'of the panel 1. At the extreme opposite end of the spindle 12, and adjacent the back side of the block 2', is mounted a fixed collar 14, forming a support or hub arm 15, and circumferent'ially of the block.

A hinge pin 17 connects the arm and linger, the parts thus connectedproviding an articulated`contact member. This finger is fur'- thermore curved slightly to conform with the curvature of the block, and' terminates at its free end. in an inturned V-shaped point 16,H adapted to engage the helical groove of the block. It is obvious vfrom the foregoing description and from the drawings, that the spindle 12 is capable'of being rotated by the 'operator through the medium of the knob 13, thus carrying the arm 15 in a circular path with the V-shaped contact point 16 engaging the helical grooves cut in the ang nular face of the block in the manner clearly shown in Figure 4, said Ifinger 16, by reasonof its pivotal connection with the `arm 15, being free to swing about the axis of the pivot pin 17 as its point 16a traverses the block inthe rotation of the contact arm in eitherdirection.l f

Lying withinthe V-shaped grooves 2'f1 is the resistance elementof the device, consisting of a single length of wire 18 which is transformed into the form of a coil by wrapping it around the block, following the helical groove' or path. One extremity of the resistance element 18 is anchored in the block at a point adjacent .to its rear side thereof means of a suitable anchor or plug 19, and forms the dead end thereof. The other extremity is similarly anchored immediately adjacent the front side of the block, and in close proximity to the conductor arm 3, said last mentioned end of the resistance element being Aanchored in the block by means of a plug 20, which in turn is electrically connected to said arm 3 by means of a short conductor21. Ascl'early-shown in Figure 4,' the pointed end of the contact finger 16 has sliding contactlwith and along the wire'18, as-the contact member is rotated in either direction, and said jnger, tracks or follows inthe groove. l f A AThe spindle 12 isalso constructed so as to have a limited degree of ,endwise motion,

' th/e purpose being to permit said spindle tobe utilized as a switch for making and breaking the circuit through the rheostat. 'The the reduced portion is advanced into said opening with the result that the contact is brokenpbetween spindle and plate, thus interrupting the current flow fromthe plate to the contact arm through the spindle. However, pulling the knob outwardly shifts .the spindle 12 'endwise, so thaty the -base of the reduced portion again contacts with the plate 4, thereby making contact between plate and spindle. The function of the sp' dle 12 as a switch member will be clearly understood from 'the description of the functionyof the rheostat, which now follows: It may be assumed, for convenience, that the' current passes into the rheostat through the conductor 6a connected with the outer terminal of the plate 4. If the spindle 12 is pulled out so that contact is made through said plate 4 in the manner above described, the

path of the current will follow thespindle rearwardly tothe arm 15 thence tothe resistance element 18 through the 'contact p int 16a of the arm16.l Passing through the resistance element, the current is con-m ducted to the upper arm 3 through the short conductor 21, thence v leaving the, rheostat through the conductor 6.

An added feature forming a useful part `of the rheostat is an indicating device shown a panel, uponfthe front face'of said panel f above the knoby 13. The scale is preferably curvilinear, having a series of graduations or unit divisions 23a marked on 'its' face, and arranged in the arc ofa circle. Intermediate the scale 23 and the spindle 12, is mounted a rotative tooth disc 24 havling a radialjpoiifter 25 projecting from its periphery. lllhe -disc meshes -with a small pinion 264 x'd to the spindle 12. It follows that. thef rotation of the spindle is transmitted to the disc 24, but at a reduced'angu: lar displacement, thus the pointer`.acts to indicate upon the scale, the corresponding' position of the contact varm with reference Ito the resistance element 18. The scale may may vbe calibrated'ior any desiredunit of electricalmeasurement. Manifestly, the ar- A .rangementof the indicating mechanism may i lbe varied, and hence theintention is to 'show ,one that would besuitable for the purpose that itis intended.

'around the periphery of the b lock 2, the

l,aid finger at the same time being swung rearwardly toward the rear face of the block. Manifestly, with each rotation of the arm by the block, a turn of the resistance element is added to the circuit, so that when the limit of rotative movement in a countcrclockwise direction is reached, the entire resistance element is thrown into circuit, and therefore the current delivered at the point of use is reduced to a minimum. Similarly, it the knob is turned in a clockwise direction, the length of the resistance unit is decreased, and therefore more and more resistancel is out out of the circuit, allowing more current to flow, and to be ultimately delivered tothe point of use. Inasmuch as it is customaryvpractice to rotate the thumb Wheel to the right for the purpose of increasing the current flow, and to the left to decrease the current flow, the threads of the block are therefore cut left handed.

In Wireless receiving apparatus, for instance, the rheostat is manipulated in the manner indicated in order to synchronize the instrument to the particular Wave length that the operator wishes to receive. Hence, by increasing or decreasing the resistance, this synchronism of Wave lengths is established. By the use of a rheostat in which the contact member lias sliding contact along the resistance element, and the path of contact coincides with the path of the current, very minute adjustments can be obtained, and the increase and decrease of resistance accomplished very gradually, and Without abrupt fluctuations, which, as in the radiophone apparatus, is very audible and distracting when magnified through the head phones.

The introduction of a switch as an element of the rheostat permits the device to perform a double function with the manipulation -of a single manually operated element; namely, a thumb Wheel. In this Way thev operation of the apparatus is greatly simplified, and the expense and cost of parts vmaterially minimized.

Having described the structure of the device, its'function and advantages, I claim as my invention:

l. A rheostat colnprising a cylindric block of non-conductive material, having a helical groove cut in the face thereof, a resistance element consisting of a length of Wire surrounding said block and lying within said groove, a contact member extending circumferent'ally with respect to the face of said block, and engaging at its free end within the groove, and in electrical contact with said resistance element, and means for imparting rotation to said contact member,

A rheostat comprising a cylindric block of nou-conductive material adapted to be mounted in fixed position, and provided with V-thrcads formed in the annular face thereof, a resistance element lying in and following the grooves formed by said thread, and a rotative contact member adapted to follow said grooves in contact with said resistance element, and to traverse the annular face of said block in the rotation of said contact member about said block. A

A rheostatcomprising a cylindric block of non-conductive material adapted to be mounted in fixed position, and provided with V-threads formed in the annular face thereof, a resistance element lying in and following the grooves formed by said thread, and a rotative contact member comprising an artfculated arm having a contact point adapted to track Within said groove in contact with said resistance element, and to traverse the face of said block in the rotation of said contact member.

4. A rheostat comprsing a cylindric block 4of non-conductive material having a helical groove formed in the annular face thereof, a resistance Wire lying within said groove, a rotative spindle arranged axially of sa-d block, a radial arm mounted 'on said spindle` and terminating adjacent the periphery of said block, and a contact finger pivotally connected With said arm, its free end tracking Within said groove in contact With said resistance wire, and a knob at one end of said spindle for manually rotating the same.

5. A rheostat comprising acylindric block of non-conductive material having a helical groove formed in the annular face thereof, a rcsstance Wire lying Within said groove, a rotative spindle arranged axially of said block, an arm fixed to one end of said spindle and extending radially of said block and bent transversely at its end, parallel to the face of said block, a finger pivotally connected to said transverse portion of the arm, and arranged oircumferentially of said block, the free end of said finger tracking in said groove in contact with said resistance, Wire, and a knob at the other end of said spindle.

A rheostat comprising a cylindric block of non-conductive material, and having a helical groove formed in the annular face thereof, a resistance wire lying in said groove, a spindle jeurnalled axially of said block, a radial arm mounted on said spindle adjacent said block, a contact finger pivotally connected with said arm, and adapted to track in said groove in contact with said VWire, conductor plates mounted upon said block, on-e connected with one end of said Wire, and the other being apertured to engage said spindle, and a knob for manually rotating said spindle.

7. A rheostat comprising a block of non? conductive material having a helical groove formed in the annular face thereof, a resiste ance wire lying within said groove, .an end? wise shiftable and rotative spindle journ-alled axially in said'block, a radial contact arm mounted on said spindle, and4 adapted to track in said groove in contact with said wire, a conductor connected with one end of condu'ctive material, having a. helical groove formed in the annular face thereof, a resistance wire lying within said groove, an endwise shiftable and rotative Spindle jour nailed Vaxially in said block, a Contact arm mounted on'said Spindle, and adapted to track in said groove in contact- With said wire, a knob mounted at one end of said spindle, a conductor connected with one end of said resistance wire, Aa conductor plate fixed to one side of said block, and having an apertured end portion adapted in one position of .endwise movement of said spindle to have electrical contact therewith, said spindle having a reduced portion adjacent said point of contact, whereby the shifting of said spindle into another position separates said Spindle and plate, breaking the circuit therethrough.

9.'A rheostat comprising a block of nonconductive material having -a helical groove formed in the annular face thereof, a resistance wire lying within said groove, a spindle journalled in said block and capable of limited endwise movement, a radial contact arm mounted in said shaft, and having contact with said wire', a conducfor connected with one end of said Wire, a conductor plate secured to one side of said block, and providedwith a bifurcated end portionadapted col foiucontact with a' cylindric portionof saidspindle, and a reduced portion adjacent said f plaie engaging portion, and coacting with I said 4plate to'brealr the circuit. through said spindle when the latter is shifted endwise to bring said reducedportion into the plane of said plate. a

lO. A rheostat comprising a cylindric blockhaving a helical groove formed in the surface thereof, a resistance wire lying within said groove and having one end thereof connected with one terminal of the rheostat, a spindle journalled in said block, and adapted for limited endwise movement, an articulated contact member mounted on saidspin- .groove in contact with said resistance element, .a fixed scale mounted on said block, a pointer journalled on said block adjacent said scale, and intermediate driving and reducing gears connecting Vsaid 'Spindle and pointer.

12. A rheostat comprising a cylindric block of non-conductive material having a helical groove formed in its annular face, a resistance element lying in said groove, a rotative spindle journalled in'said block provided with a contact arm engaging said groove in contact with said resistance element, a fixed scale, a toothed disc journalled on said block intermediate said scale and spindle,land provided with a pointer adapted to register with said scale, and a toothed pinion mounted on said spindle and meshing with said disc.

13. In apparatus of the class described,a drum having a resistance wire Wound helically thereon, a spindle mounted axially of the drum, a contact o erable by rotation of the spindle and tracking along the wire, a terminal connected to one end of the wire, another terminal associated with the spindle all so constructed and arranged that the terminals may be electrically connected or disconnected by a longitudinal movement of the spindle, along its axis.

14. Ini'apparatus of the class described, a drumof non-conducting material having a V shaped helical groove therein; a tine wire lying in the bottom of said groove, a pointed contact resting on said wire in said groove, 'a means for tracking the contact along the wire, and circuit connections to one end of the wire and the contact.

15'. In apparatus of the class described, a drum of non-conducting material having a V shaped helical groove therein, aline wire lying at the bottom of the groove, a resilient pointed contact linger yieldingly pressed lagainstthe wire, and control means for tracking the contact finger back and "forth i the rheostat.

along the wire' by turnin thecontrol means.,

16. In apparatus eoft e class` described,-:-centrially of the axis of said stationaryl and in combination, a drum, a resistance wire coiled helically upon the druin, a shaft. mounted for revolution axially of the drum,"

an arm on the shaft, a contact finger mov-V ably mounted on the arm, and adapted to-k track 'along the wire, means for manually turning the sha-ft, ysaid turning means and arm being on opposite sides of the drum.

17. In apparatus of theclassvdescribed,y

and in combination, al panel, a drum 'having a flat end secured to the rear face vofv the panel, a resistance wire,heli cally wound upon the drum, a shaft revolubly mounted in the drum and passing through the panel, a control knob on the shaft in front of the panel, an arm at the opposite'end ofthe shaft, a contact finger on the arm adapted to track along the wire. v

18. A rheostat of the lclass describedcomdrical surface with a helical groove, a resistance wire tautly wound helically around said drum and disposed in' said groove, a shaft'disposed with its axis concentric with the axis of said drum, said shaft being capable of both rotary and' axial movement'- with respect tosaid drum, and a contact 'device carried by said shaft, said contact device bein adapted to move both'around and lon itu inally of said drum and to follow sai resistance wire in continuous contact therewith to vinclude more or less ofthe resistance wire in the ci'rcuitcontrolled 19. A rheostat of the classy described, comprising al stationary drum, rovided 'on its outer cylindrical surface with a helical groove a resistance wire tautly woundaroun said drum anfd disposed in sad m -name'thi's 11t ay JOHN]l groove, va shaft Vjournaled'for rotation condrum, `and a contact devicecarried by said .,shaft,'said`contact device being adapted to move around ink said oove and longitudi-` inally of said druman to follow said resistcontinuous contact therewith to include prising a drum provided onits outer cylin-v` more or less of -the'resistance wire in the circuit controlled by the rheostat. 21. A rheostat of the class deseribed, comprisingI a stationary drum provlded with a cylindrical surface having a helical groove therein, high. resistance conducting means disposed in said helical groove, ashaft journaled for rotation substantially concentriand a contact :device carried by said shaft,

cally of the axis of'said cylindrical surface,

the end of said contact device being adapted to move 'around in said groove and lonb ,gitudinally of said drum and to follow said y 1 vtinuous contact therewith to include moreor gh' resistance conducting means in conless of the high resistance conductin means' -in'the circuit controlled by the said r leostatiy In witness'whereof, I hereunto subscribe da of March,A.. D. 1922. OTT JENKINS. 

